In a gas turbine, hot gases of combustion flow from an annular array of combustors through a transition piece for flow along an annular hot gas path. Turbine stages are typically disposed along the hot gas path such that the hot gases of combustion flow from the transition piece through first-stage nozzles and buckets and through the nozzles and buckets of follow-on turbine stages. The turbine buckets may be coupled to a plurality of rotor disks comprising the turbine rotor, with each rotor disk being mounted to the rotor shaft for rotation therewith.
A turbine bucket generally includes a root portion configured to be coupled to one of the rotor disks of the turbine rotor and an airfoil extending radially outwardly from the root portion. In general, during operation of a gas turbine, the hot gases of combustion flowing from the combustors are directed over and around the airfoil. As such, bucket airfoils are prone to damage from thermally induced stresses and strains. For example, airfoils may be subject to creep and other forms of material relaxation and/or property degradation as the components undergo a range of thermo-mechanical loading conditions within the gas turbine. This may be particularly true for turbine buckets formed from composite materials (e.g., ceramic matrix composite materials), as such turbine buckets are not typically air-cooled and, thus, may experience high temperatures throughout the airfoil.
Accordingly, there is a need for a turbine blade assembly that reduces the likelihood of creep and other forms of material relaxations and/or property degradation from occurring within an airfoil during operation of a gas turbine.